Entity detection system and method for monitoring an area

ABSTRACT

An entity detection method and system are provided for monitoring an area. The method comprises providing an illuminated band extending continuously along an extremity of the area; providing an optical detector having an image sensor adapted to capture an image, the illuminated band being viewable by the image sensor and being capturable in the image, a space between the band and the image sensor being part of the area; storing a detection threshold; analyzing the image to detect a discontinuity in the continuous illuminated band apparent on the image, comparing the detected discontinuity to the detection threshold; and indicating a status of the area to be one of a presence of an entity and an absence of the entity based on the comparing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase entry of PCT Application No.PCT/IB2010/055785, entitled “ENTITY DETECTED SYSTEM AND METHOD FORMONITORING AN AREA”, filed on Dec. 13, 2010; which in turn claimspriority of US provisional patent application Ser. No. 61/286,175 filedon Dec. 14, 2009, and of US provisional patent application Ser. No.61/286,172 filed on Dec. 14, 2009, the specifications of which arehereby incorporated by reference.

TECHNICAL FIELD

The present invention generally relates to entity detection systems andmore particularly to an entity detection system for detecting thepresence of an entity in a monitored area delimited by the illuminationof a lighting system.

BACKGROUND OF THE ART

Detecting the presence of an entity in a specific area is a need whicharises in many different situations. Applications which make use of sucha detection include intrusion in a security perimeter or detection of anentity in an area having systems, or actuators, that can be dangerousfor this entity.

Several detection systems have been developed and installed for sensingan entity in a specific area or for detecting an entity in a area thatincludes some risk for that entity. Some systems use motion sensors andassess changes in ambient temperature produced by a moving entity. Theyare therefore not designed to detect a moving entity since itstemperature is typically the same as the ambient temperature. Also,motion sensors are not capable of detecting a stationary entity. Anotheralternative is to use an infrared source and an infrared receiver todetect the presence of an entity. Detection occurs when an entityinterferes with the reception by the receiver of the emitted infraredsignal. Even if several sources and receivers are installed to cover thesurface of the monitored area, gaps always exist, leaving areas notcovered by the entity detection system. Thus, there is a need forimprovements in the detection of entities in monitored areas.

An example of where this need is felt is in the area of mobile storagesystems. The optimization of space for storing different kinds ofmaterial is the main benefit of mobile storage systems. However, using amobile storage system implies security issues. When the need to open anaisle explicitly requires to close another aisle, it is very importantto detect the presence of an entity in the aisle before closing it.Thus, there is a need for improvements in the detection of moving andstationary entities in mobile storage systems.

SUMMARY

A proposed solution includes using lighting as a component of the entitydetection system which can be used to provide illumination for the user,send a feedback for the detection and delimit the area.

Examples of applications where such a solution could be used includemobile storage units, elevators, aisles, fences and walls delimitingmonitored areas, no-trespassing areas, for example in industrialsettings, light curtains applications, etc.

One aspect of the invention provides an entity detection method formonitoring an area. The method comprises providing an illuminated bandextending continuously along an extremity of the area; providing anoptical detector having an image sensor adapted to capture an image, theilluminated band being viewable by the image sensor and being capturablein the image, a space between the band and the image sensor being partof the area; storing a detection threshold; analyzing the image todetect a discontinuity in the continuous illuminated band apparent onthe image, comparing the detected discontinuity to the detectionthreshold; and indicating a status of the area to be one of a presenceof an entity and an absence of the entity based on the comparing.

In one embodiment, the illuminated band is a continuous distributedlight source.

In one embodiment, the continuous distributed light source is a strip ofLight-Emitting-Diodes.

In one embodiment, the strip of Light-Emitting-Diodes comprises adiffuser.

In one embodiment, the continuous distributed light source is a lightpipe with optic fiber.

In one embodiment, the continuous illuminated band is a retro-reflectiveband, wherein the optical detector further comprises a punctual lightsource emitting light toward the retro-reflective band.

One aspect of the invention provides an entity detection system formonitoring an area. The system comprises an illuminated band extendingcontinuously along an extremity of the area; an optical detector havingan image sensor adapted to capture an image, the illuminated band beingviewable by the image sensor and being capturable in the image, a spacebetween the band and the image sensor being part of the area; a memoryfor storing a detection threshold; and a processor receiving the imagefrom the image sensor, having an image analyzer for analyzing the imageto detect a discontinuity in the continuous illuminated band apparent onthe image, a discontinuity comparator for comparing the detecteddiscontinuity to the detection threshold; and a status indicator forindicating a status of the area to be one of a presence of an entity andan absence of the entity based on the comparing.

One aspect of the invention provides a mobile storage having a mobilestorage unit extending along a longitudinal axis, with a detection side;an opposing unit extending substantially parallel to the longitudinalaxis, having a detection side facing the detection side of the mobilestorage unit; at least one detection duo having: an illuminated bandextending continuously along the longitudinal axis of a first one of thedetection side of the mobile storage unit and the detection side of theopposing unit; an optical detector provided at a second one of thedetection side of the mobile storage unit and the detection side of theopposing unit, the second one being different from the first one; theilluminated band being viewable by the optical detector; the mobilestorage unit being movable between a closed position wherein thedetection sides of the mobile storage unit and the opposing unit arejuxtaposed and an open position wherein the mobile storage unit and theopposing unit are spaced-apart and a longitudinally extending aisle isdefined therebetween.

In one embodiment, the mobile storage further comprises a an opticaldetector having a memory for storing a detection threshold; a processorhaving an image analyzer for analyzing the image to detect adiscontinuity in the continuous illuminated band apparent on the image,determining a discontinuity length of the discontinuity, comparing thediscontinuity length to the detection threshold; and indicating a statusof the aisle to be presence of an obstacle if the discontinuity lengthis longer than the detection threshold and indicating the status of theportion of the aisle to be absence of an obstacle if the discontinuitylength is shorter than the detection threshold.

In one embodiment, there are two detection duos, the detection side ofthe mobile storage unit and the detection side of the opposing unit eachhaving the illuminated band extending continuously along thelongitudinal axis, the detection side of the mobile storage unit and thedetection side of the opposing unit each having the optical detector.

Still another aspect of the detection system for a mobile storage systemprovides at least a first mobile storage unit having at least twoopposed sides; an opposing object selected from the group consisting ofa wall, a second mobile storage unit and a stationary storage unit, adetection side of the opposing object facing the first mobile storageunit on one aisle side of the at least two opposed sides, an aisle beingdefined between the first mobile storage unit and the opposing object,the aisle having a first aisle end and a second aisle end; the detectionsystem comprising : for the aisle side of the at least two opposed sidesof the first mobile storage unit, a first continuous illuminated bandprovided along the length of the aisle side; a first optical detectorprovided at the first aisle end of the first band facing the detectionside and able to acquire and transmit a first image; for the detectionside, a second continuous illuminated band provided along the length ofthe detection side, viewable by the first optical detector, wherein afull length of the second continuous illuminated band is apparent on thefirst image when no obstacle is present in the aisle and the aisle is inan open position; a second optical detector provided at the second aisleend of the second band facing the aisle side and able to acquire andtransmit a second image, wherein a full length of the first continuousilluminated band is apparent on the second image when no obstacle ispresent in the aisle and the aisle is in an open position; a controlunit having a receiver for receiving the first image and the secondimage from the first optical detector and the second optical detector; amemory for storing a detection threshold; a processor having a firstimage analyzer for analyzing the first image to detect a firstdiscontinuity in the second continuous illuminated band apparent on thefirst image, determining a first discontinuity length of the firstdiscontinuity, comparing the first discontinuity length to the detectionthreshold; and indicating a status of a first portion of the aisle to bepresence of an obstacle if the first discontinuity length is longer thanthe detection threshold and indicating the status of the first portionof the aisle to be absence of an obstacle if the first discontinuitylength is shorter than the detection threshold, a second image analyzerfor analyzing the second image to detect a second discontinuity in thefirst continuous illuminated band apparent on the second image,determining a second discontinuity length of the second discontinuity,comparing the second discontinuity length to the detection threshold;and indicating a status of a second portion of the aisle to be presenceof an obstacle if the second discontinuity length is longer than thedetection threshold and indicating the status of the second portion ofthe aisle to be absence of an obstacle if the second discontinuitylength is shorter than the detection threshold, a status determiner fordetermining a status of the aisle to be occupied if at least one of thestatus of the first portion and the status of the second portion is thepresence of an obstacle and for determining a status of the aisle to beempty if both of the status of the first portion and the status of thesecond portion is the absence of an obstacle.

Still another aspect of the invention provides a detection method for amobile storage system having at least a first mobile storage unit havingat least two opposed sides; an opposing object selected from the groupconsisting of a wall, a second mobile storage unit and a stationarystorage unit, a detection side of the opposing object facing the firstmobile storage unit on one aisle side of the at least two opposed sides,an aisle being defined between the first mobile storage unit and theopposing object, the aisle having a first aisle end and a second aisleend; for the aisle side of the at least two opposed sides of the firstmobile storage unit, a first continuous illuminated band provided alongthe length of the aisle side; a first optical detector provided at thefirst aisle end of the first band facing the detection side and able toacquire and transmit a first image; for the detection side, a secondcontinuous illuminated band provided along the length of the detectionside, viewable by the first optical detector, wherein a full length ofthe second continuous illuminated band is apparent on the first imagewhen no obstacle is present in the aisle and the aisle is in an openposition; a second optical detector provided at the second aisle end ofthe second band facing the aisle side and able to acquire and transmit asecond image, wherein a full length of the first continuous illuminatedband is apparent on the second image when no obstacle is present in theaisle and the aisle is in an open position; the detection methodcomprising : receiving the first image and the second image from thefirst optical detector and the second optical detector; storing adetection threshold and the first image and the second image; analyzingthe first image to detect a first discontinuity in the second continuousilluminated band apparent on the first image, determining a firstdiscontinuity length of the first discontinuity, comparing the firstdiscontinuity length to the detection threshold; and indicating a statusof a first portion of the aisle to be presence of an obstacle if thefirst discontinuity length is longer than the detection threshold andindicating the status of the first portion of the aisle to be absence ofan obstacle if the first discontinuity length is shorter than thedetection threshold, analyzing the second image to detect a seconddiscontinuity in the first continuous illuminated band apparent on thesecond image, determining a second discontinuity length of the seconddiscontinuity, comparing the second discontinuity length to thedetection threshold; and indicating a status of a second portion of theaisle to be presence of an obstacle if the second discontinuity lengthis longer than the detection threshold and indicating the status of thesecond portion of the aisle to be absence of an obstacle if the seconddiscontinuity length is shorter than the detection threshold,determining a status of the aisle to be occupied if at least one of thestatus of the first portion and the status of the second portion is thepresence of an obstacle and for determining a status of the aisle to beempty if both of the status of the first portion and the status of thesecond portion is the absence of an obstacle.

In one embodiment, the method further comprises storing an intensitythreshold, analyzing the first image and the second image to detect anintensity for each the first and second discontinuity, comparing eachthe intensity to the intensity threshold, indicating the status to bethe presence of the obstacle if the intensity is lower than theintensity threshold and indicating the status to be the absence of theobstacle if the intensity is higher than the intensity threshold.

Still another aspect of the present invention provides a mobile storagehaving a mobile storage unit extending along a longitudinal axis, havinga detection side with an illuminated band extending continuously alongthe longitudinal axis, and an optical detector; an opposing unitextending substantially parallel to the longitudinal axis, having adetection side facing the detection side of the mobile storage unit,having an illuminated band extending continuously along the longitudinalaxis and viewable by the optical detector of the mobile storage unit,and having an optical detector spaced-apart from the optical detector ofthe mobile storage unit along the longitudinal axis, the illuminatedband of the mobile storage unit being viewable by the optical detectorof the opposing unit, the mobile storage unit being movable between aclosed position wherein the detection sides of the mobile storage unitand the opposing unit are juxtaposed and an open position wherein themobile storage unit and the opposing unit are spaced-apart and alongitudinally extending aisle is defined therebetween.

In one embodiment, the illuminated bands of the mobile storage unit andthe opposing unit extend from a first end to an opposed second end ofthe longitudinally extending aisle.

In one embodiment, the optical detector of the opposing unit is locatedat the first end and the optical detector of the mobile storage unit islocated at the second end.

In one embodiment, the illuminated band of the opposing unit is entirelyviewable by the optical detector of the mobile storage unit and theilluminated band of the mobile storage unit is entirely viewable by theoptical detector of the opposing unit.

In one embodiment, the system further comprises a control unit having areceiver for receiving a mobile unit image from the optical detector ofthe mobile storage unit and a opposing unit image from the opticaldetector of the opposing unit; a memory for storing a detectionthreshold; a processor having a mobile unit image analyzer for analyzingthe mobile unit image to detect a first discontinuity in the continuousilluminated band of the opposing unit apparent on the mobile unit image,determining a first discontinuity length of the first discontinuity,comparing the first discontinuity length to the detection threshold; andindicating a status of a first portion of the aisle to be presence of anobstacle if the first discontinuity length is longer than the detectionthreshold and indicating the status of the first portion of the aisle tobe absence of an obstacle if the first discontinuity length is shorterthan the detection threshold, an opposing unit image analyzer foranalyzing the opposing unit image to detect a second discontinuity inthe continuous illuminated band of the mobile unit apparent on theopposing unit image, determining a second discontinuity length of thesecond discontinuity, comparing the second discontinuity length to thedetection threshold; and indicating a status of a second portion of theaisle to be presence of an obstacle if the second discontinuity lengthis longer than the detection threshold and indicating the status of thesecond portion of the aisle to be absence of an obstacle if the seconddiscontinuity length is shorter than the detection threshold, a statusdeterminer for determining a status of the aisle to be occupied if atleast one of the status of the first portion and the status of thesecond portion is the presence of an obstacle and for determining astatus of the aisle to be empty if both of the status of the firstportion and the status of the second portion is the absence of anobstacle.

Another aspect of the invention provides a mobile storage having amobile storage unit extending along a longitudinal axis, having adetection side with an illuminated band extending continuously along thelongitudinal axis; an opposing unit extending substantially parallel tothe longitudinal axis, having a detection side facing the detection sideof the mobile storage unit, having an optical detector, the illuminatedband of the mobile storage unit being viewable by the optical detectorof the opposing unit, the mobile storage unit being movable between aclosed position wherein the detection sides of the mobile storage unitand the opposing unit are juxtaposed and an open position wherein themobile storage unit and the opposing unit are spaced-apart and alongitudinally extending aisle is defined therebetween.

In one embodiment, the mobile storage further comprises a control unithaving a receiver for receiving a opposing unit image from the opticaldetector of the opposing unit; a memory for storing a detectionthreshold; a processor having an opposing unit image analyzer foranalyzing the opposing unit image to detect a second discontinuity inthe continuous illuminated band of the mobile unit apparent on theopposing unit image, determining a second discontinuity length of thesecond discontinuity, comparing the second discontinuity length to thedetection threshold; and indicating a status of a second portion of theaisle to be presence of an obstacle if the second discontinuity lengthis longer than the detection threshold and indicating the status of thesecond portion of the aisle to be absence of an obstacle if the seconddiscontinuity length is shorter than the detection threshold.

Another aspect of the invention provides a mobile storage having amobile storage unit extending along a longitudinal axis, having adetection side with an optical detector; an opposing unit extendingsubstantially parallel to the longitudinal axis, having a detection sidefacing the detection side of the mobile storage unit, having anilluminated band extending continuously along the longitudinal axis andviewable by the optical detector of the mobile storage unit, the mobilestorage unit being movable between a closed position wherein thedetection sides of the mobile storage unit and the opposing unit arejuxtaposed and an open position wherein the mobile storage unit and theopposing unit are spaced-apart and a longitudinally extending aisle isdefined therebetween.

In one embodiment, the mobile storage further comprises a control unithaving a receiver for receiving a mobile unit image from the opticaldetector of the mobile storage unit; a memory for storing a detectionthreshold; a processor having a mobile unit image analyzer for analyzingthe mobile unit image to detect a first discontinuity in the continuousilluminated band of the opposing unit apparent on the mobile unit image,determining a first discontinuity length of the first discontinuity,comparing the first discontinuity length to the detection threshold; andindicating a status of a first portion of the aisle to be presence of anobstacle if the first discontinuity length is longer than the detectionthreshold and indicating the status of the first portion of the aisle tobe absence of an obstacle if the first discontinuity length is shorterthan the detection threshold.

Another aspect of the invention provides a detection system for a mobilestorage system having at least one mobile storage unit having at leasttwo opposed sides; an opposing object selected from the group consistingof a wall, a second mobile storage unit and a stationary storage unit, adetection side of the opposing object facing the mobile storage unit onone aisle side of the at least two opposed sides, an aisle being definedbetween the first mobile storage unit and the opposing object, the aislehaving a first aisle end and a second aisle end; the detection systemcomprising : for the aisle side of the at least two opposed sides of thefirst mobile storage unit, a continuous illuminated band provided alongthe length of the aisle side; for the detection side, an opticaldetector facing the aisle side and able to acquire and transmit animage, wherein a full length of the first continuous illuminated band isapparent on the image when no obstacle is present in the aisle and theaisle is in an open position; a control unit having a receiver forreceiving the image from the optical detector; a memory for storing adetection threshold; a processor having an image analyzer for analyzingthe image to detect a discontinuity in the continuous illuminated bandapparent on the image, determining a discontinuity length of thediscontinuity, comparing the discontinuity length to the detectionthreshold; and indicating a status of the aisle to be presence of anobstacle if the discontinuity length is longer than the detectionthreshold and indicating the status of the portion of the aisle to beabsence of an obstacle if the discontinuity length is shorter than thedetection threshold.

Another aspect of the invention provides a detection system for a mobilestorage system having at least one mobile storage unit having at leasttwo opposed sides; an opposing object selected from the group consistingof a wall, a second mobile storage unit and a stationary storage unit, adetection side of the opposing object facing the mobile storage unit onone aisle side of the at least two opposed sides, an aisle being definedbetween the mobile storage unit and the opposing object; the detectionsystem comprising : for the aisle side of the at least two opposed sidesof the mobile storage unit, an optical detector facing the detectionside and able to acquire and transmit a image; for the detection side, acontinuous illuminated band provided along the length of the detectionside, viewable by the optical detector, wherein a full length of thecontinuous illuminated band is apparent on the image when no obstacle ispresent in the aisle and the aisle is in an open position; a controlunit having a receiver for receiving the image from the opticaldetector; a memory for storing a detection threshold; a processor havingan image analyzer for analyzing the image to detect a discontinuity inthe continuous illuminated band apparent on the image, determining adiscontinuity length of the discontinuity, comparing the discontinuitylength to the detection threshold; and indicating a status of the aisleto be presence of an obstacle if the discontinuity length is longer thanthe detection threshold and indicating the status of the portion of theaisle to be absence of an obstacle if the discontinuity length isshorter than the detection threshold.

Throughout this specification, the term “non-visible” is intended to bea synonym of the terms “invisible” and “nonvisible” and to be an antonymto the word “visible”. It should be understood that “visible light”refers to light emitted at wavelengths which are visible to the humaneye. Similarly, “invisible light” refers to light emitted at wavelengthswhich are not visible to the human eye.

Throughout this specification, the term “area” is intended to mean avolume of space, such as an horizontal volume of space near the floor ofa room, a vertical volume of space delimited by a door framing (such asthe volume of space created when an elevator door is open), a volume ofspace of an aisle created between two units of a mobile storage unitsystem, etc.

Throughout this specification, the term “entity” is intended to includeany moving or stationary entity, having a detectable presence in anarea, such as a person, an animal, an object, an environmental particle,a gas, a liquid, a particle such as dust, etc. If the area to bemonitored is to be protected against the presence of a person or animal,this person or animal can be referred to as an “intruder”. If the areato be monitored is to be kept free of any object, person or animal, theobject, person or animal present in the area can be referred to as an“obstacle”. Intruders and obstacles are entities.

Throughout this specification, the term “environmental particle” isintended to include any particle detectable in the air or on the groundand which is typically caused by an environmental, chemical or naturalphenomenon. It includes fog, rain, snow, smoke, gas, smog, hail, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus generally described the nature of the invention, referencewill now be made to the accompanying drawings, showing by way ofillustration a preferred embodiment thereof and in which:

FIG. 1 shows an example embodiment of the entity detection system in amonitored area;

FIG. 2 comprises FIGS. 2A, 2B and 2C which show a top view of amonitored area with different configurations for the lighting system;

FIG. 3 shows an example embodiment of the entity detection system in amobile storage system;

FIG. 4 comprises FIGS. 4A and 4B which show a top view of an aisle withtwo sections of a mobile storage system integrating the entity detectionsystem, in FIG. 4A, an entity is detected by the first opticaldetection, in FIG. 4B, an entity is detected by each optical detector;

FIG. 5 shows a top view of an aisle with a series of multiple opticaldetectors provided on each side of the aisle;

FIG. 6 shows a block diagram illustrating main components of an exampleembodiment of the entity detection system for monitoring an area;

FIG. 7 shows the basic motorized structure of an example mobile storagesystem equipped with an example entity detection system;

FIG. 8 comprises FIG. 8A and FIG. 8B (photograph) which shows an exampleembodiment using a retroreflector and a photograph of the captured imageof the retroreflective band;

FIG. 9 is an example embodiment using a retroreflector and a mirrorfilm.

FIG. 10 is a flow chart of main steps of an example embodiment of thedetection method;

FIG. 11 comprises FIGS. 11A (photograph) and 11B (photograph) which showphotographs of example images captured by the optical detectors, in FIG.11A, there is no entity present, in FIG. 11B, three entities arepresent;

FIG. 12 (photograph) is a photograph of an example image where the wholeilluminated band is apparent and the non-illuminated sides of the bandare also apparent; and

FIG. 13 (photograph) is a photograph of an example image where theilluminated band is created by a series of punctual sources, namely astrip of LEDs.

It will be noted that throughout the appended drawings, like featuresare identified by like reference numerals.

DETAILED DESCRIPTION

FIG. 1 shows a monitored area 10, with a permanent feature 12 of thearea which is monitored by an entity detection system 22 for detecting amoving entity within the monitored area. As will be readily understood,the permanent feature 12 of the area is present in the example monitoredarea 10 of FIG. 1 to ensure a complete description of the exampleembodiment. In another example, such a permanent feature 12 of the areamay take on different shapes and sizes, may include many permanentfeatures 12 or need not be present. Other entities present in themonitored area, which are not permanent features of the area will bereferred to as entities 30.

The entity detection system 22 has at least one optical detector 24 andat least one distributed light source 26 illuminating and delimiting themonitored area 10 with visible or invisible light 28. The opticaldetector 24 detects the illumination of the distributed light source 26.

The optical detector 24 and the distributed light source 26 aretypically installed on a side of the physical structure of the monitoredarea, close to or on the floor. As will be readily understood, otherconfigurations are possible. For example, the illuminated band may beprovided near the ground and the optical detector may be provided at alevel higher than that of the band. It can be hung from the ceiling, forexample. The distributed light source 26 emits visible light (red,green, white, etc) or invisible light (infrared for instance).Typically, the distributed light source 26 is made of a strip of LEDs, alight pipe with optic fiber or other light source able to distribute theillumination on the monitored area. The distributed light source coverssections of the monitored area. To improve the diffusion ofillumination, a diffuser (not shown) can be placed in front of thedistributed light source 26. The diffuser is particularly useful whenthe distributed light source 26 is made by using LEDs or other punctualsources. Several types of diffusers or lenses can be used to improve theillumination function of the system. However, for detection purposes,the illumination may be provided by a series of punctual sources spacedapart by a small distance, for example a few centimeters, or a wholelight source band along the side of the monitored area to cover thedetection area. The distributed light source and the diffuser areinstalled on the side of the monitored area structure or on the floorusing a casing (ex.: plastic, aluminum extrusion, etc.) to facilitatethe installation and the maintenance (to change a section ofillumination for instance), and to protect the components of the source.This casing can also be used as a diffractive component. In that case,the light is diffracted on the holder and the optical sensor receivesthis diffracted light instead of directly receiving illumination fromthe sources.

Different colors may be used as architectural elements or as aretroaction means for the users. For example, in a surveillanceapplication, a green light illumination around the monitored area mayindicate that there is no entity in the monitored area while a red lightillumination may indicate the presence of an entity. A person enteringthe monitored area may visually understand the status of the monitoredarea. For example, in a mobile storage unit application, a green lightillumination on both sides of an aisle may indicate that there is noentity in the aisle while a red light illumination may indicate thepresence of an entity. A person wishing to close an aisle to openanother may visually understand the status of occupancy of the aisle.

Other sources may also be used typically at the entrance of themonitored area or aisle to indicate its status. For example, a whitesource may be distributed throughout the monitored area or aisle and redand green sources may be provided at the entrance of the area or aisleas indicators.

It is possible to generate specific pulses using specific sources(markers such as marker 1100 in figures 11A and 11B) at each end of thedistributed light band to indicate the beginning and the end of the bandor each segment. This generation of pulses may be useful whencalibrating or during a diagnosis for example. Other specific sources(markers) can be added in a segment to indicate the position of themoving storage unit (x % close). The position of the marker in the image(x, y) will change when the aisle is closing.

Other sources may be installed in other areas to increase the height ofthe detection in the aisle or the height of the detection area or tohave a stealth detection area. For example, an IR distributed lightsource may be installed at the top of a storage unit (or on one edge ofa shelf) or all around a fence. This source then becomes a second lineof detection for the entity detection system. Several sources can beinstalled and become multiple lines of detection for the entitydetection system.

The optical detector 24 is typically installed just above thedistributed light source but, as discussed above, can also be providednear the ceiling, hung from a wall or any object facing the distributedlight source. The optical detector is preferably installed in a box andtypically a window protects the components (optical and electronic).

Usually, all the cables to supply power and to communicate with theentity detection system come from the structure delimitating theperimeter (for example, the surrounding wall).

FIG. 2A shows a top view of a monitored area. An optical detector 24 isused to detect light 28 from the distributed light source 26 whichsurrounds monitored area. This sensor has typically a wide Field Of View40 (FOV) to see the continuous long strip of illumination,. Normally,this FOV has to be close to 90° to cover the surface of the monitoredarea and can be up to 360°. When an entity 42 is between the opticaldetector 24 and the distributed light source 26, an importantattenuation in the illumination is detected by the optical detector 24.

FIG. 2B shows an example configuration with two optical detectors 24 andone distributed light source 26 with permanent feature 12. With thisconfiguration, the monitored area does not suffer from a blind spot madeby the permanent feature 12 and the system can still detect an entity42.

FIG. 2C shows a configuration with one optical detector 24 with a verylarge FOV 40 (more than) 180° covering the whole surface illuminated bythe distributed light source 26. It is therefore able to detect anentity 42.

FIG. 3 shows an application example for the entity detection system andmethod. In this example application, the entity detection system is usedto detect the presence of an entity in an open aisle of a mobile storagesystem 310. A mobile storage system 310 having several mobile storageunits 312 and one stationary unit 330. A wall (not shown) can also beprovided at an end of the system 310. An open aisle 314 permits accessto storage space 316 (ex.: shelves). A drive mechanism or arrangement(not shown and typically using an electrical motor) allows the movementof a mobile storage unit 312 on a mounting rail 318 and permits closingan aisle to open another aisle. Control panel 320 (ex.: keypad) is aninput to a controller unit (not shown) which can be used by a user tocontrol the movement of a storage unit 312. By closing an aisle, a usercan open another aisle and access a specific storage space. Each side ofa storage unit 312 has an entity detection system 322 for detecting anentity in an open aisle. The open aisle is therefore the monitored area.

The entity detection system 322 has at least one optical detector 324and at least one distributed light source 326 illuminating the openaisle 314 with visible or invisible light 328. The optical detector 324on one side of an open aisle detects the illumination of the distributedlight source 326 from the other side of the open aisle, namely from aneighboring or opposing section of the mobile storage system.

The optical detector 324 and the distributed light source 326 aretypically installed on a side of the mobile storage unit 312 (typicallynear the bottom of the structure), or in some cases at the bottom of awall or of a stationary unit 330. The distributed light source 326 emitsvisible light (red, green, white, etc) or invisible light (infrared forinstance). Typically, the distributed light source 326 is made of astrip of LEDs, a light pipe with optic fiber or other light source ableto distribute the illumination on the aisle between two storage units ofthe mobile storage system or one storage unit and a wall. Thedistributed light source covers the whole length of the aisle.

In case of emergency, if visible illumination is used, the visibleillumination indicates which aisles are open and therefore facilitatesevacuation or signaling to the surrounding people.

The optical detector 324 is preferably installed in a box and typicallya window protects the components (optical and electronic).

Usually, all the cables to supply power and to communicate with theentity detection system use a dedicated space close to the mountingrails 318 or are installed at the top of the mobile storage system.

FIG. 4A shows a top view of an open aisle with two sections 312, 330 ofa mobile storage system. An optical detector 324 is used to detect light328 from the distributed light source 326 on the opposite side of theaisle. This sensor has a relatively wide Field Of View 340 (FOV) to seethe continuous long strip of illumination, for instance 30 feet, in anarrow aisle (typically, 4 feet or less for commercial application, 10feet or less for industrial application). Normally, this FOV has to beclose to 90° to cover the surface of the open aisle. When an entity 342is between the optical detector 324 and the distributed light source326, an important attenuation in the illumination is detected by theoptical detector 324.

FIG. 4B shows an example configuration with two optical detectors andtwo distributed light sources. The optical detector on one side detectsthe illumination on the other side and covers half of the surface of theopen aisle. Typically, when several optical detectors (and distributedlight sources) are installed, optical detectors are daisy-chained withone master and slave(s).

FIG. 5 shows a configuration with several optical detectors anddistributed light sources for a very long aisle, typically used forindustrial application. More precisely, FIG. 5 shows an aisle with adetector system made with six optical detectors and 6 distributed lightsources. Each optical sensor acts as part of a network covering thewhole surface of the aisle, even if aisle is very long.

FIG. 6 presents a block diagram of an example embodiment of the entitydetection system 622. The entity detection system 622 has at least oneoptical detector 624 and at least one distributed light source 626. Thedistributed light source 626 has at least one light source 650. Thelight source 650 can have one or more solid-state lighting devices, LEDsfor instance (visible or non-visible). The light source 650 illuminatesthe environment directly or via a diffuser, a lens and/or an opticalfilter 654. The light source 650 is connected to a source driver 652, soas to be driven into producing continuous illumination or pulsedillumination. In the case of pulsed illumination with visible light, itshould be preferable to have a pulse frequency high enough not to beperceivable by the human eye (typically more than 20 Hz). Pulsedillumination can improve the detection performance with a higher peak ofillumination during integration of the image sensor and lower continuouspower.

The source driver 652 can adjust the level of illumination. The opticaldetector 624 may be adapted to obtain information on the ambient lightto optimize the adjustment. An ambient light sensor (not shown) can alsobe used.

The source driver 652 can also measure the current and the voltage ofthe light source for monitoring and diagnosis purposes and eventuallyfor sharing this information with the digital processor unit. The sourcedriver 652 can be controlled by the Digital Processor Unit 660 orNetwork and external controller B.

The illumination can be turned off when the detection function is notused in the monitored area or when the aisle is completely closed in themobile storage unit example. Visible illumination can also be controlledto emit low frequency pulses to inform users of different status. Forinstance, light pulse at low frequency (ex.: 1 pulse/sec) may indicatean alarm.

The optical detector 624 has an image sensor 656 which has the functionto detect the illumination light from the distributed light source 626.The image sensor 656 is for example any CMOS or CCD array sensor, coloror monochrome. The image sensor 656 has a lens/window 658 collectinglight emitted by the distributed light source 626 with a generally awide FOV, typically between close to 90° and 360°, covering the surfaceof the monitored area. The surface of the monitored area can be thelength of the aisle in the mobile storage unit example.

A window is useful to protect the image sensor, the lens and theelectronic components. A casing is typically provided to protect thecomponents. When the entity detection system is turned off, the opticaldetector 624 can be put on a hold mode. The optical detector 624 can bea camera, a smart camera or a camera with a processing unit adapted tocarry out some processing of the images.

Optical filters (not shown) can be provided with the image sensor 656 toattenuate ambient background light emitted from others sources of lightthereby enhancing the performance of the detection as a function of thecolor of the illumination. Digitalization of image information is madeby the image sensor 656 and is transferred to a digital processor unit660.

Digital processor unit 660 is connected to the source driver 652 and tothe image sensor 656, and controls parameters such as the optical powerof light pulses, the frequency of pulses, synchronization with the imagesensor 656, synchronization from other optical sensors and/ordistributed light source, the integration time, the sample rate, etc.When the light is pulsed, the digital processor can integrate an imageduring the illumination and another image without illumination to beimmune from the background light.

The digital processor unit 660 has a processing unit (e.g., CPU, DSP,microcontroller) so as to interpret the data from the image sensor 656.

Accordingly, information about the presence of an entity in themonitored area is determined by the digital processor unit 660 as afunction of the relation between the detected light data from thedistributed light source in the field of view and an importantfluctuation of the illumination from a detected entity A.

The digital processor unit 660 also performs the calibration process.Image analysis permits to determine the section of the distributed lightsource representing the beginning and the end of the monitored area.

Diagnosis of the distributed light source 626 can be performed by thedigital processor unit 660. The intensity of the illumination and thequality of the line are stored in database memory 666. Each time acommand to start the diagnostic procedure is needed, the image sensordetects the distributed light source and the digital processor unitevaluates the intensity and the continuity of the line, detecting if anypart of the distributed light source has failed or if any permanentfeature is present in the FOV. The presence of permanent features can beconfirmed by the user of the entity detection system or can bedouble-checked by using more than one optical detector to obtain morethan one perspective. If a small part of the illumination is broken,compensation can be determined. Results of the diagnosis can be sent tothe network.

In the example of a mobile storage unit, each time an aisle is openedand before any detection of an entity entering the aisle, the imagesensor detects the distributed light source and the digital processorunit evaluates the intensity and the continuity of the line, detectingif any part of the distributed light source has failed.

A specific diagnosis source (not shown), for instance a small IR LED,can be integrated in the optical detector 624 to determine the state ofthe window of the optical sensor module. During calibration, the levelof reflection from the sensor window can be measured and stored in thedatabase memory. During operation, the system can measure the reflectionof the window using this specific diagnosis source and compare it withthe calibration data stored in the database memory. A high level ofreflection can mean that the window is dirty and may have an impact onthe operation of the system. Diagnosis of the window can be sent to theexternal controller.

The optical detector 624 has sensors 662 connected to the digitalprocessor unit 660. Sensors 662 can include temperature sensors,accelerometers, inclinometers, smoke sensors and humidity sensors, forexample. For instance, an accelerometer can be helpful in detecting themovement of the storage unit (opening or closing). Those sensors 662 areuseful during installation and operation. Optional optical sources (notshown) like infrared or color LED for example, can be integrated in theoptical detector for detection and status purposes. Optional detectorsources may be used as an indicator for the position of the opticaldetector or for indicating the status of the section covered by theoptical detector (presence or absence of an entity). Optional opticalsources can be seen and detected by other optical detector placedelsewhere in the monitored area. Optional detector sources can be placedat the end of the storage unit. Optional optical sources can be seen anddetected by the optical detector on the other side of the aisle.

The optical detector 624 has a power supply and interface 664. Theinterface section is connected to digital processor unit 660 andcommunicates with the network and the external controller B (RS-485,wireless, power line, Ethernet, PoE, CAN bus, relay contact, wirelesslink, etc.). Direct communication between the optical detectors is alsopossible. Information is related to the detection of an entity in themonitored area and to other types of measurement (temperature, etc.).The network and the external controller can also program, calibrate,send information about the monitored area (permanent features,activation or deactivation of the security of the monitored area, etc)and control the entity detection system 622. The network and theexternal controller can send information about the movement of thestorage unit. Parameters like thresholds, intensity of illumination,etc, can be sent and stored in the database memory 666. The interfacealso controls the activation (On/Off) and synchronization of the sourcedriver 652. Switches 668 can be used to reset the entity detectionsystem, start a calibration sequence and/or to determine an address on aunit.

During installation, the interface can be used to receive an image fromthe optical detector to confirm that the FOV of the image sensor coversall the illumination of the monitored area. During operation, imagesfrom the optical detector can be sent to the external controller forsecurity purpose. For instance, if the entity detection system detectsan entity, it can send an image of the situation of the monitored area.Then, further actions can be done by the external controller based onthat information.

When a monitored area is wide and long, several systems can be installedto cover the space for the detection purpose. Several optical sensorsand distributed light sources can be connected in a network.

FIG. 7 shows the basic motorized structure of an example mobile storagesystem equipped with an example entity detection system. In thisparticular view of an example basic motorized structure 704 of anexample mobile storage system, the shelving of the unit is omitted forclarity. Shelving support members 706 are shown. The illuminated band702 extends continuously along the longitudinal axis of the detectionside of the mobile storage unit. The optical detector 700 is provided atone end of the mobile storage unit, just above the illuminated band 702.The optical detector 700 is provided in a casing with a window facingthe illuminated band of the neighboring mobile storage unit.

The mobile storage unit is movable between a closed position wherein thedetection sides of the mobile storage unit and the opposing unit arejuxtaposed and no aisle is created and an open position wherein themobile storage unit and the opposing unit are spaced-apart and alongitudinally extending aisle is defined therebetween, thelongitudinally extending aisle being the area. The opposing unit can bea wall, a second mobile storage unit or a stationary storage unit.

A drive arrangement 708 for movement of the mobile storage unit, along apath, one of toward and away from the opposing unit, to open and closethe aisle is shown. As will be readily understood, a controller for thedrive arrangement controlling the movement of the mobile storage unit isnot shown. Similarly, a user input switch for the controller foractivating the drive arrangement for movement of the mobile storage unitis only shown in FIG. 3 (control panel 320). The alarm generator forgenerating an alarm if the image analyzer determines the status of thearea to be presence of an entity is not shown but the controller wouldblock movement of the mobile storage unit upon the alarm using the drivearrangement 708.

Others embodiments are possible. FIG. 8 comprises FIG. 8A and FIG. 8B(photograph) which shows an example embodiment using a retroreflectorand a photograph of the captured image of the retroreflective band. InFIG. 8A, the distributed light source is replaced by a retroreflector800 and a punctual source with a large field of illumination isinstalled close to the optical detector 802 and emits light in directionof the retroreflector. The retroreflector reflects light back to itssource with a minimum scattering of light. This light reflected back isdetected by the optical detector with the same effect than a distributedlight. FIG. 8B shows the light reflected back from a retroreflector asseen by the optical detector.

FIG. 9 is an example embodiment using a retroreflector and a mirrorfilm. FIG. 9 shows a retroreflector strip 904 installed on one side ofthe aisle with an optical sensor 902 at each end including a punctualsource. A mirror, typically a mirror film 900, is installed on the otherside. In that embodiment, the light from the punctual source isreflected on the mirror through the retroreflector. Then, theretroreflector reflects light back to the mirror and the mirror reflectsthis light back to the optical detector.

Other sources like a laser, for example a laser emitting a line, can beused to illuminate the aisle and be detected by the optical detector.

FIG. 10 is a flow chart of main steps of an example embodiment of thedetection method. It details typical operation of the entity detectionsystem. Calibration 500 sets all the parameters for the operation. Thisstep is triggered by the network and the central controller or by aswitch initiating the calibration. During calibration, the monitoredarea must be clear without any movable entity present inside of themonitored area (only permanent features may be present). In the case ofa mobile storage unit, the aisle must be open without any entity inside.The calibration 500 activates the distributed light source of themonitored area and takes images with the optical sensor on the area.Calibration with several distributed light sources and several opticaldetectors covering the entire area can be done at the same time. Duringthe calibration 500, the optical detector has to search and find a lineof illumination and determine the region of interest for detectionpurposes. The detected line can be continuous or made by separate dotsof illumination in accordance with the distributed light source (spacebetween dots must be inferior to the dimension of a detected entity).Depending on optical components, the line detected by the image sensorcan be curved. The position of the line of illumination is stored in thedatabase memory. Depending on the type of the surface, reflection on thefloor can be detected by the optical sensor. FIG. 5A shows a typicalimage of the illumination with reflection on the floor. This reflectioncan be rejected by the analysis of the image (reflection is positionedlower than the line of illumination and is typically lower inintensity). The line of illumination represents the entire surface ofthe area and the optical detector has been installed to cover the entiresurface of the illumination. If the illumination is pulsed, the imagesensor can be synchronized with the illumination. The sensitivity of theimage sensor can be set at that stage.

At acquisition 502, the image sensor acquires at least an image(synchronize if needed with pulsed light) and transfers it to theprocessor. At extraction 504, the processor extracts the line ofillumination and compares it with the information from the calibrationdata and thresholds. At analysis 506, the processor analyses the line ofillumination and when it finds a region wider than X (or f(x)) with alevel of intensity lower than Y (or f(y)), then an entity is detected.If not, the processor considers that there is no entity detected. Theprocessor can control the lighting using the detection result (it can,for example, change the illumination color, generate an alarm, etc.).Information about the presence or the absence of an entity can be sentto the external controller by the network. X is a parameter varying infunction of the angle of the FOV.

In the embodiment where specific pulses using specific sources aregenerated for use as markers (such as marker 1100 in figures 11A and11B) at each end of the distributed light band to indicate the beginningand the end of the band or segments of the band, the entity detectedmethod consequently further comprises providing at least one marker onsaid illuminated band, said marker indicating an end of said illuminatedband; storing a marker image profile; analyzing said image to detect amarking pulse in said continuous illuminated band apparent on saidimage, comparing said marking pulse to said marker image profile toconfirm that said marking pulse is an image of said marker; anddetermining a location of an end of said continuous illuminated band onsaid image when said marking pulse is said image if said marker.

FIG. 11 comprises FIGS. 11A (photograph) and 11B (photograph) which showphotographs of example images captured by the optical detectors, in FIG.11A, there is no entity present, in FIG. 11B, three entities arepresent. In FIG. 11B, the entities cause discontinuities in the line ofillumination. A first entity at the left hand side of the image causesone discontinuity and an entity, namely a person, at the right hand sideof the monitored area causes two discontinuities (his legs). The size ofthe discontinuity is dependant on the size of the entity and alsodependant on the position in the FOV. In that case, the entity on theleft hand side is closer to the optical detector and will cause a widerdiscontinuity when compared to a discontinuity located further from theoptical detector at the end of the monitored area.

FIG. 12 (photograph) is a photograph of an example image where the wholeilluminated band is apparent and the non-illuminated environment of theband, on both sides, is also apparent. In FIG. 12, the exampledistributed light source is installed to cover a surface delimited bytwo walls (at a corner of these two walls). The system is able todetermine the beginning and the end of the distributed light sourcebased on the clear level of illumination in comparison to ambient lightlevel. The entity detection system determines a region of interest andstores the shape, the length, the height and the typical intensity ofthe distributed light source when it illuminates. Those parameters aredependant on the position in the Field Of View (relationship between theFOV and the distance between the distributed light source and theoptical detector). The intensity Y is related to the intensity of theillumination (Y may also vary depending of the angle and the distance).

FIG. 13 (photograph) is a photograph of an example image where theilluminated band is created by a series of punctual sources, namely astrip of LEDs. When using punctual sources (like LEDs) and particularlywhen the aisle is closing (or opening), the distribution of the line ofillumination is a sequence of bright spots separated by a distance (interms of pixels) that increases (decreases if opening) when thedistributed light source is approaching (or moving away If opening) theoptical detector. The parameter X (or f(x)) can be adapted to thatsituation to be able to detect an entity when the aisle is closing(opening) without generating any false alarm.

Once an entity is detected, the processor can track and classify thisentity. For instance, an entity can be classified as an entering entity.This can be done by detecting the position of the entity at time TO,storing its position, and detecting the entity at time T1, anddetermining the displacement of this entity. For instance, an entityentering in the monitored area will cause a fluctuation on the line ofillumination detected by the optical detector in a specific section onthe FOV. When this entity moves further into the monitored area, theposition of the entity changes in the FOV. For a configuration withseveral optical detectors, the entity can move up to the point wherethis entity can enter in the FOV of the second optical detectorinstalled on other section of the monitored area. This entity can leavethe monitored area at another end and the optical detector at this othersection will detect this leaving entity or, this entity can go back andleave the monitored area by the same end and will be detected again bythe optical detector at that end. The signature and behavior of anobject versus a person are different and can be used as information forimproving the security of the system. The number of entering entitiescan be used for counting the number of times presence of an entity isdetected in the monitored area (ex.: statistic purposes, continuouspresence detection, etc). Each entity can be tracked and detected untilthe entity leaves the monitored area (exiting).

For instance, an entity entering in one side of the aisle is clearlydetected by the optical detector installed in that side. When thisentity moves further into the aisle, the position of the entity changesin the FOV of the optical detector up to the point where this entity canenter in the FOV of the second optical detector installed on the otherend of the aisle. This entity can leave the aisle at the other end andthe optical detector at this other end will detect this leaving entityor, this entity can go back and leave the aisle by the same end and willbe detected again by the optical detector at that end.

The tracking of an entity can also be useful to detect an entitystanding in the middle of the monitored area and climbing up the wall orother structure in the monitored area. In that case, the entity stillcan be in the monitored area and the system will continue to report thatsomeone is in the area even if the line of illumination is notdisrupted. In that case, sending image information from the opticaldetector to the external controller can be useful particularly forsecurity purpose.

For instance, three areas can be set, two on both sides of the aisle andone covering the middle of the aisle. The tracking process can determinethe position of the entity and the system evaluates an entity is leavingthe aisle or climbing in the middle of the aisle.

Adding other(s) distributed light source(s) at a higher level in themonitored area is another way to detect an entity, for example a person,climbing in the area or to help covering the detection of an entity at ahigher level. The camera has a vertical field of view permitting thedetection of a distributed light source at a several feet of height.Vertical distributed light sources can also be installed at the ends ofthe monitored area to cover entry/exit, a door for instance. For thosedistributed light sources, visible or infrared illumination can be used.The entity detection system can also be installed higher to see a topview of the surface and the distributed light source.

The entity detection system can receive information from the externalcontroller, such as information about permanent features and activationor deactivation of the monitored area. An important aspect of the entitydetection system is the detection of an entering entity in the monitoredarea when a security activation has commenced. An example of such anapplication would be when the entity detection system is used in anelevator and triggers the door controller to activate the door. Theentity detection system could immediately send information to theexternal door controller about the detection of the presence of anentity to stop or begin movement of the elevator door.

The entity detection system can receive information from the externalcontroller. For instance, information about the opening and closing ofan aisle can be received and used by the detection unit. When the aisleis closing, the optical sensor will detect an increasing length ofillumination. An important aspect when closing an aisle is the detectionof an entering entity. The entity detection system must immediately sendthis information to the external controller to stop the movement of thestorage unit.

When an aisle is opening, the entity detection system can perform anauto diagnosis particularly on the quality of the line of illumination,on the position of the region of interest and on several parameters,until an entity enters in the aisle. The results of the diagnosis can besent to the external controller.

A reset of the entity detection system may be triggered manually fromthe optical detector (switch) or by external controller when in doubtthat there may be an entity in a monitored area while the entitydetection system reports otherwise. In some cases, it may be useful toreset the system. For example, if the system has detected an entity andlost the detection in the middle in the area, the entity detectionsystem may consider that this entity is still in the area even if theentity is no longer present. In that case, a user can perform a manualreset by using a switch on the optical detector or by the panel control.The system will restart and may diagnostic itself before entering in itsnormal operation mode.

The entity detection system has several mobile storage, industrial,commercial and security applications. In an industrial area protection,the entity detection system can clearly define a protected area usingthe distributed light. It acts like a light curtain and detects anyentity which drops on this area or any entity coming into the area whenit is not permitted or when it is dangerous. It is also useful todetermine a safety area when the use of a robot or other moving machinecan potentially cause harm to an entity in a specific area.

Elevator door protection is another application where the entitydetection system can improve the safety of passengers by sending afeedback using different colors of illumination. In that case, thedistributed light source is installed around the door structure and canbe seen by the user. An optical detector detects the presence of thepassenger in the aperture and sends this information to the elevatordoor controller. When the door controller wants to close the door, itchanges the color of the distributed light source to warn the userbefore starting to close the door. The controller will close the dooronly if no entity is detected in the aperture.

In the application of security intrusion detection covering a largearea, the distributed light can be installed on the wall or on the fencedelimiting the perimeter of the monitored area. At least one opticaldetector is installed and detects any entity in the monitored area. Thisinformation is sent to the external controller (alarm, image, etc).Users can configure different sections to determine safety area versusareas where activities are permitted.

The entity detection system can be installed on existing mobile storagesystems or provided during installation.

While illustrated in the block diagrams as groups of discrete componentscommunicating with each other via distinct data signal connections, itwill be understood by those skilled in the art that the illustratedembodiments may be provided by a combination of hardware and softwarecomponents, with some components being implemented by a given functionor operation of a hardware or software system, and many of the datapaths illustrated being implemented by data communication within acomputer application or operating system. The structure illustrated isthus provided for efficiency of teaching the described embodiment.

The embodiments described above are intended to be exemplary only. Thescope of the invention is therefore intended to be limited solely by theappended claims.

We claim:
 1. An entity detection system for monitoring an area, saidarea created between a mobile unit and an opposing unit, said mobileunit extending along a longitudinal axis and having a detection side,said opposite unit extending parallel to the longitudinal axis andhaving a detection side facing the detection side of the mobile unit,the mobile unit being movable between an open positon wherein the mobileunit and the opposing unit are spaced-apart and a longitudinallyextending aisle is defined therebetween and a closed position whereinthe detection sides of the mobile unit and the opposing unit arejuxtaposed and said aisle collapses, said longitudinally extending aislebeing said area, said entity detection system comprising: a distributedlight source adapted to provide an illuminated band, said illuminatedband extending longitudinally continuously along the longitudinal axisof a first one of said detection side of said mobile unit and saiddetection side of said opposing unit; at least one marker provided on aterminal minor portion of said illuminated band, a major portion of saidilluminated band disposed adjacent to the minor portion and not havingsaid at least one marker, said at least one marker generating a markingpulse using a specific source indicating an end of said illuminatedband, wherein the marking pulse is indicative of a position of themobile unit; an optical detector, said optical detector being providedat a second one of said detection side of said mobile unit and saiddetection side of said opposing unit, said second one being differentthan said first one, said optical detector having an image sensoradapted to capture an image, the illuminated band and said at least onemarker being viewable by the image sensor and being capturable in saidimage, a space between said distributed light source and said imagesensor being part of said area; a memory for storing a detectionthreshold and a marker image profile, wherein said detection thresholdincludes an intensity amplitude threshold and a length threshold; and aprocessor receiving said image from said image sensor, said processorhaving an image analyzer for analyzing said image to detect adiscontinuity and the marking pulse in said continuous illuminated bandapparent on said image and to determine an intensity amplitude and alength of said discontinuity, said discontinuity being caused by apresence of an entity in said area, between said distributed lightsource and said image sensor, said entity blocking light emitted fromsaid illuminated band toward said image sensor, said processor capableof comparing said marking pulse to said marker image profile to confirmthat said marking pulse is an image of said marker and of determining alocation of an end of said continuous illuminated band on said image,said location of said end of said continuous illuminated band on saidimage being dependent upon said position of said mobile unit withrespect to said opposing unit; said processor further comprising adiscontinuity comparator for comparing said intensity amplitude of saiddetected discontinuity to said intensity amplitude threshold and saidlength of said discontinuity to said length threshold, said intensityamplitude threshold and said length threshold being a function of saidposition of said mobile unit with respect to said opposing unit and fordetermining a status of said area to be a presence of an entity if saidlength of said discontinuity is longer than said length threshold andsaid intensity amplitude of said discontinuity is smaller than saidintensity amplitude threshold; and said processor also comprising astatus indicator for indicating said status of said area to be one ofsaid presence of said entity and an absence of said entity based on saidcomparing said intensity amplitude and said length and on said locationof said end of said continuous illuminated band.
 2. The entity detectionsystem as claimed in claim 1, wherein the illuminated band is entirelyviewable by the optical detector.
 3. The entity detection system ofclaim 1, further comprising a plurality of illuminated bands extendingcontinuously along all extremities of said area.
 4. The entity detectionsystem of claim 1, further comprising a plurality of optical detectors.5. The entity detection system of claim 1, further comprising an alarmgenerator for generating an alarm if said status indicator indicatessaid status of said area to be presence of an entity.
 6. The entitydetection system of claim 5, further comprising a visual indicator forindicating said status of said area based on said alarm.
 7. The entitydetection system of claim 1, wherein said illuminated band emits atleast one of visible light and invisible light.
 8. The entity detectionsystem as claimed in claim 6, wherein said visual indicator is a colorof visible light illumination of said illuminated band.
 9. The entitydetection system of claim 1, wherein said mobile unit is a mobilestorage unit of a mobile storage.
 10. The entity detection system asclaimed in claim 9, wherein said opposing unit is one of a wall, asecond mobile storage unit and a stationary storage unit.
 11. The entitydetection system of claim 1, further comprising a second opticaldetector and a second illuminated band, said detection side of saidmobile unit and said detection side of said opposing unit each havingsaid illuminated band extending continuously along the longitudinalaxis, said detection side of said mobile unit and said detection side ofsaid opposing unit each having said optical detector.
 12. The entitydetection system as claimed in claim 11, wherein said processor receivestwo images, one image from each said optical detector; said imageanalyzer analyzes, said discontinuity comparator compares and saidstatus indicator indicates for each image of said two images; whereinsaid processor further comprises a status determiner for determining astatus of said aisle to be occupied if at least one of said statusindicated by said status indicator is said presence of an entity and fordetermining a status of said aisle to be empty if both of said statusindicated by said status indicator is said absence of an entity.
 13. Theentity detection system of claim 1, further comprising a drivearrangement for movement of the mobile unit, along a path, one of towardand away from the opposing unit, to open and close the aisle, acontroller for the drive arrangement controlling the movement of themobile unit, a user input switch for the controller for activating thedrive arrangement for movement of the mobile unit, said detection unitfurther comprising an alarm generator for generating an alarm if saidimage analyzer determines said status of said area to be presence of anentity, the controller blocking movement of the mobile unit upon saidalarm.
 14. An entity detection method for monitoring an area, said areacreated between a mobile unit and an opposing unit, said mobile unitextending along a longitudinal axis and having a detection side, saidopposite unit extending parallel to the longitudinal axis and having adetection side facing the detection side of the mobile unit, the mobileunit being movable between an open positon wherein the mobile unit andthe opposing unit are spaced-apart and a longitudinally extending aisleis defined therebetween and a closed position wherein the detectionsides of the mobile unit and the opposing unit are juxtaposed and saidaisle collapses, said longitudinally extending aisle being said area,said entity detection method comprising: providing a distributed lightsource adapted to generate an illuminated band, said illuminated bandextending longitudinally continuously along the longitudinal axis of afirst one of said detection side of said mobile unit and said detectionside of said opposing unit; providing at least one marker provided on aterminal minor portion of said illuminated band, a major portion of saidilluminated band disposed adjacent to the minor portion and not havingsaid at least one marker, said at least one marker generating a markingpulse using a specific source indicating an end of said illuminatedband, wherein the marking pulse is indicative of a position of themobile unit; providing an optical detector, said optical detector beingprovided at a second one of said detection side of said mobile unit andsaid detection side of said opposing unit, said second one beingdifferent than said first one, said optical detector having an imagesensor adapted to capture an image, the illuminated band and said atleast one marker being viewable by the image sensor and being capturablein said image, a space between said distributed light source and saidimage sensor being part of said area; storing a detection threshold anda marker image profile, wherein said detection threshold includes anintensity amplitude threshold and a length threshold; analyzing saidimage to detect a discontinuity in said continuous illuminated bandapparent on said image and to determine an intensity amplitude and alength of said discontinuity, said discontinuity being caused by apresence of an entity in said area, between said distributed lightsource and said image sensor, said entity blocking light emitted fromsaid illuminated band toward said image sensor; analyzing said image todetect the marking pulse in said continuous illuminated band apparent onsaid image; comparing said detected discontinuity to said detectionthreshold by comparing said intensity amplitude of said detecteddiscontinuity to said intensity amplitude threshold and said length ofsaid discontinuity to said length threshold, said intensity amplitudethreshold and said length threshold being a function of said position ofsaid mobile unit with respect to said opposing unit; comparing saidmarking pulse to said marker image profile to confirm that said markingpulse is an image of said marker; determining a location of an end ofsaid continuous illuminated band on said image, said location of saidend of said continuous illuminated band on said image being dependentupon said position of said mobile unit with respect to said opposingunit; determining a status of said area to be a presence of an entity ifsaid length of said discontinuity is longer than said length thresholdand said intensity amplitude of said discontinuity is smaller than saidintensity amplitude threshold; and indicating said status of said areato be one of said presence of said entity and an absence of said entitybased on said comparing said intensity amplitude and said length and onsaid location of said end of said continuous illuminated band.
 15. Theentity detection method as claimed in claim 14 wherein a plurality ofdiscontinuity are detected in said analyzing step.
 16. The entitydetection method of claim 14, wherein said mobile unit is a mobilestorage unit of a mobile storage.
 17. The entity detection method asclaimed in claim 14, wherein said storing said image comprises storingsaid two images, one image from each said optical detector; saidanalyzing, comparing and indicating comprise analyzing, comparing andindicating for each image of said two images; further comprisingdetermining a status of said aisle to be occupied if at least one ofsaid status is said presence of an entity and for determining a statusof said aisle to be empty if both of said status is said absence of anentity.
 18. The entity detection system of claim 1, wherein theilluminated band is a retro-reflective band, the system furthercomprising a punctual light source emitting light toward theretro-reflective band.